In the prior art, medical imaging systems, in particular x-ray systems are known, which are characterized by a great flexibility in the movements of the image recording devices about the patient. In the case of an x-ray system, these moveable parts are in particular the x-ray detector and the x-ray tube. The so-called C-arm x-ray systems particularly enjoy great popularity, in which the x-ray tube and the detector are fixed in each instance to opposing arms of a C-arm, which can be moved arbitrarily about the patient in order to allow x-ray recordings from any projection direction. By varying the distance between the x-ray detector and the patient, the enlargement can furthermore be changed and the image distorting scattered radiation can be minimized. Systems such as Siemens AG's AXIOM Artis for instance are used in particular as angiography systems. Quasi-tomographical 3D images are increasingly generated with such x-ray devices, with which the C-arm is moved about the patient through approximately 180°. With a cycle of this type, also referred to as DynaRun, some of the moveable parts are rotated about the patient at a considerable speed. One problem with these types of imaging systems with moveable parts is that the moveable parts may collide with the patient. Protective mechanisms must thus be introduced in order to rule out any risks to the patient.
With the above-cited AXION Artis system, a protective zone enclosing the patient is defined for instance. If a C-arm approaches this protective zone, it is clearly slowed down so as to avoid the risk of a collision. This protective zone is identical for all patients and has roughly the form of an ellipsoid arranged over the patient support. With thin patients in particular, this protective zone is thus often distanced far from the actual patient surface. It thus often takes an unnecessarily long time to start a specific angulation of the C-arm.
In the case of devices made by Philips, some of the capacitative sensors which detect the proximity of the patient and thereupon slow down the movement of the C-arm are positioned on the C-arms. However, these sensors only have a minimal coverage, so that the movement of the C-arm is also assumed to be slowed down here when it enters an accepted protective zone.
As a final safety feature, both systems have mechanical position indicators, which immediately stop the movement of the moveable parts when a patient is actually contacted.